Cassava Morphological Characteristics and trait

evaluation at different breeding stages

2015 AGRA Training Workshop for Research Technicians in Breeding

Kulakow/Parkes/AinaCassava Breeding Unit, IITA

OUTLINE• Importance of Cassava• Cassava biology and taxonomy• Production statistics• cassava breeding approach• cassava agronomical considerations• Growth morphology• Morphological characterization of cassava• Class activity• Format for different trial stages• Data collection at different trial stages• Selection index• Take home tips

Importance of Cassava• Cassava originates from Latin America and was introduced into Africa

over 400 years ago

• feeds more than 500 million people in Africa, Asia, and Latin America (Roa et al., 1997)

• is an important food security crop in Africa and is fast becoming a commercial crop

• Now recognized as a suitable commodity to drive Africa’s economic development

• Used in various food forms, animal feed and industrial raw material (starch, ethanol, adhesives etc),

Biology and taxonomy of Cassava• perennial shrub that grows erect to heights between 1-4m

• propagated vegetatively using cuttings and through botanical seeds for breeding activity

• shoot system: stem, leaves and reproductive inflorescence

• root system: fibrous or feeder roots and tuberous roots

class - Dicotyledoneae family- Euphorbiaceae, (7,200 species) genus - Manihot species- M. esculenta (cultivated form), M. flabellifolia and M. peruviana. (wild form) family- Euphorbiaceae: Hevea brasilensis latex, while others produce

oil (Ricinus communis

Leaf and inflorescence• palmate leaves bearing 3 to 9 lobes and covered with a shiny,

waxy epidermis.

• Cassava is monoecious, bearing separate female and male flowers on the same plant, flowers are borne together in the inflorescences, with the pistillate flowers beneath the staminate with female flowers opening one to two weeks before the male flowers on the same inflorescence

• The female flowers open for approximately one day, and the stigma is receptive throughout that time

inflorescence

• Flowering may also be influenced by environmental factors with some clones not flowering in some locations, flowering in others while some do not flower at all

• Female flowers have 5 sepals, which can be red, yellow, or purple, and a sticky stigma which secretes nectar on the day the flower opens

• each male flowers has 10 stamens, borne in two rings and smaller in size compared to female flowers, approximately 5 mm, but more numerous

more about cassava • Cassava is grown on a variety of soils, and it tolerates marginal, low-fertility,

acid soils better than many other staple crops

• Cassava responds favourably to added fertilizer, especially k, but over-fertilization, especially with nitrogen, can increase leaf growth at the expense of root formation

• removes less nitrogen and phosphorous per tonne of dry matter (DM) produced than other common crops

• Competition with weeds, PPD , flowering challenges and biotic constraints are considered major limitation to cassava

• Disease control is mostly accomplished through the use of resistant varieties, selecting planting materials from disease free plant and early removal of diseased plants

Area under cultivation Area Cultivated 2010 2011 2012 2013 % (million ha)

World 19.5 20.5 20.8 20.7Africa 13.0 13.8 10.0 14.2 68.4

Nigeria 3.5 3.7 3.9 3.9 18.6DRC 1.9 2.2 2.2 2.2 10.6Ghana 0.9 0.9 0.9 0.9 4.2Angola 0.9 1.1 1.1 1.2 5.6Mozambique 1.2 1.2 0.8 0.8 3.8Tanzania 0.9 0.7 1.0 1.0 4.6Uganda 0.4 0.4 0.4 0.4 2.1

Asia 3.9 4.1 4.2 4.2 20.2Thailand 1.2 1.1 1.4 1.4 6.7Indonesia 1.2 1.2 1.1 1.1 5.2Vietnam 0.5 0.6 0.6 0.5 2.6India 0.2 0.2 0.2 0.2 1.0

Latin America 2.4 2.3 2.3 2.1 10.3Brazil 1.8 1.7 1.7 1.5 7.3Colombia 0.2 0.2 0.2 0.2 1.1Paraguay 0.2 0.2 0.2 0.2 0.9

Source: FAO,2014

Cassava Production (MMT)Cassava Production 2010 2011 2012 2013 % (million Mt)

World 243.05 261.76 269.12 276.72Africa 134.4 147.41 149.4 157.98 57.1

Nigeria 42.53 52.4 54 54 19.5DRC 15.01 15.02 16 16.5 6.0Ghana 13.5 14.25 14.54 14.55 5.3Angola 13.85 14.33 10.63 16.41 5.9Mozambique 9.73 10.09 10.05 10 3.6Tanzania 4.54 4.64 5.46 5.4 2.0Uganda 5.28 4.75 4.92 5.22 1.9

Asia 74.95 80.47 88.97 88.22 31.9Thailand 22 21.91 29.84 29.3 10.6Indonesia 23.91 24 24.17 23.93 8.6Vietnam 8.59 9.89 9.74 9.74 3.5India 8.05 8.07 8.74 7.23 2.6

Latin America 31.94 32.09 29.19 28.77 10.4Brazil 24.96 25.34 23.04 21.22 7.7Paraguay 2.62 2.45 1.68 2.8 1.0Colombia 2.08 2.13 2.25 2.48 0.9

Source: FAO,2014

Cassava Yield (t/ha)Cassava Average Yield 2010 2011 2012 2013 % (t/ha)

World 12.4 12.8 12.9 13.3Africa 10.3 10.7 10.7 11.1 -16.5

Nigeria 12.2 14.0 14.0 14.0 5.2DRC 8.1 6.9 7.3 7.5 -43.8Ghana 15.4 16.0 16.7 16.7 25.3Angola 15.6 13.4 10.0 14.1 5.3Mozambique 7.8 7.8 13.2 12.8 -3.9Tanzania 5.2 6.3 5.7 5.7 -57.4Uganda 12.7 11.2 11.5 12.0 -9.9

Asia 19.3 19.7 21.0 21.1 58.1Thailand 18.8 19.3 21.9 21.8 63.6Indonesia 20.2 20.3 21.4 22.5 68.4Vietnam 17.3 17.7 17.7 17.9 34.1India 34.8 36.5 38.6 35.0 162.0

Latin America 12.9 13.0 12.9 12.9 -3.1Brazil 13.9 14.6 13.6 13.9 4.3Paraguay 14.8 13.5 9.8 16.0 19.9Colombia 10.6 10.5 10.7 10.7 -19.7

Source: FAO,2014

Cassava Breeding Approach1. Identify desirable parents – from available germplasm

collection and also from partners IITA - over 2700 accessions of locally selected cultivars CIAT- nearly 6000 accessions

2. Generate variation: Hybridization technique (controlled crosses) Desirable parents selected for hybridization

3. Selection for desired trait characteristics meeting specific end users objective: progenies with favourable alleles selected at the seedling nursery and advanced through various breeding stages CET, PYT, AYT, and UYT

Hybridization in cassava

Female and Male flower Bagging and pollination

Fruit Seedling nursery seed

Clonal evaluation

Typical Cassava Breeding CycleSeedling nursery (SN)

(no replication)

Multi-location Uniform yield trial

(UYT)(4 replications)

Clonal evaluation (CE)(no replication)

Preliminary yield trial (PYT)

(2 replications)Advanced yield trial

(AYT)(4 replications)

Crossing Blocks – Source

Populations

National Variety Testing and

On-Farm Trials

Year 1

Year 2

Year 3

Year 4

Years 5 & 6

Multiplication and Release

NARS/PARTNERS

Years 7 & 8

Rapid

Multiplication

One-cycle ofrecombinationin 8 years.

Potential to shortened breeding cycle using genomic selection

Summary of cassava varieties Released in Nigeria (1976-2014)

S/No Year of release No. of genotypes released

1 1976 1

2 1984 1

11 1986 15

12 1988 1

13 2005 614 2006 515 2009 213 2010 4

14 2011 5

15 2012 3

16 2014 3

Total 46

agronomical considerations• Age and length of planting materials• Stem cutting • Stem storage• Timely planting • Spacing and plant population • Supply of missing plants• Fertilizer application the ‘4Rs’• Weed control• Rouging of off-types• Disease and pest control• Field evaluation and data collection• Laboratory analysis• Reporting

land preparation and weed control in cassava field

Growth morphology• Sprouting stage (5-15 DAP): First adventitious roots from the buds under

the soil within 1 week of planting (5-7 DAP), small leaves emergence at 10-12 DAP and full leaf emergence achieved at 15 DAP

• Leaf development and root system formation stage (15-90 DAP): leaves expansion with the initiation of photosynthetic process (30 DAP), growth of fibrous roots begins to replace adventitious roots and actively functioning in water and nutrient adsorption. Few fibrous becomes storage roots (60 to 90 DAP).

• Stems and leaves (canopy) establishment stage(90-180 DAP): leaves intercept most of the incident light on canopy with maximum growth rates of leaves and stems achieved with DM partitioned to leaves and stems, as storage root continues to bulk.

growth morphology cont’d• Assimilate translocation to roots stage (180-300 DAP):

Storage root bulking enhanced as assimilate is partitioned from leaves to roots with the highest rate of DM accumulation in storage roots

• Dormancy stage (300-360 DAP): Leaf production rate decreased, leaf fall increases as shoot vegetative growth is terminated. Translocation of starch to root is maintained. Plant completes 12 month cycle, to be followed by a new period of vegetative growth when moisture becomes available

Cassava Morphological Descriptor

14: Root neck length:

Why characterization

• to determine the genetic diversity among cassava genotypes

• prerequisite for genetic improvement through the extent of genetic variation present between cultivars

• Enables the selection of diverse parental combinations and broaden genetic base of a breeding population

• high levels of diversity suggest a recombination and gene flow which can play an important role in the preservation of species diversity

Unexpanded leaf, petiole and stem color

98/0581

Dark brown silver green Silver green

Green purple; green green purple; green purple; red

Cassava Plant type

Umbrella Compact open

s/n Trait Time schedule

Phenotypic class and Score

1 unexpanded leaf color 1-3MAP 3= light green5= dark green7= purplish green9= purple

2 1st fully expanded leaf color 1-3MAP light greengreen purplepurple

3 pubescence of young leaves 1-3MAP 0=absence1=presence

4 flowering 3-6MAP 0= absence1 =presence

5 anthocyanin distribution on petiole

6MAP absenttop to bottomtotally pigmented

6 growth habit of stem 9MAP 1= straight,2= zigzag

7 stem color 9MAP 1= Silver green2= light brown/orange3= dark brown

8 Plant type 12 MAP 4= compact 3= Open 2= Umbrella1= Cylindrical

s/n Trait Time schedule

Phenotypic class and score

9 central leaf lobe shape 1-3MAP 1= ovoid2= elliptic lanceolate3= obovate lanceolate4= oblong lanceolate5= lanceolate6= straight or linear7= pandurate8= linear pyramidal9= linear pandurate10= linear hostatilobalate

10 petiole color 3-5MAP 1= yellowish green2= green3= reddish green5= greenish red7= red9= purple

Evaluation for yield parameters at harvests/n Trait Mode of

evaluationRemark/score 

1 Number Harvested  

count reflect sprouting ability

2 Root number  

count  suggest tuberization potential

3 Root Weight (Kg) 

weighing Low/medium/high fresh yld 

4 Shoot Weight (Kg) weighing Useful in estimation of HI  

5 Root Size  

visual small, medium, or large sized roots3 = small, 5 = medium, 7 = largeMarketable and unmarketable root distribution 

6 Root Shape  

visual 1 = Conical, 2 = Conical-cylindrical3 = Cylindrical, 4 = Fusiform5 = Irregular, 6 = Combination 

Schedule for scoring of vigor, sprout and diseases

Parameter Schedule Scoring scale

     Sprout 1MAP CountVigor 1MAP 3, 5 & 7CMD1 1MAP 1, 2,3,4 & 5 CMD3 3MAP 1, 2,3,4 & 5 CMD6 6MAP 1, 2,3,4 & 5      CBB3 3MAP 1, 2,3,4 & 5 CBB6 6MAP 1, 2,3,4 & 5 CGM1 & CGM2 6-9MAP 1, 2,3,4 & 5     CAD 9 9MAP 1, 2,3,4 & 5Stay green 6-9MAP  1,3,5,7,9

Selection of parents for hybridization

S/N Trait

Var1 Var 2 Var 3 Var 4

1 Stem color light green dark green purple green,

brown

2 Petiole color Light green dark green purple red3 Plant type compact open umbrella cylindrical4 Stem growth

habitupright upright Zig-zag upright

5 CMD resistance susceptible tolerant resistant tolerant6 CBB resistance susceptible tolerant resistant susceptible7 DM content high moderate low moderate8 Fyld low moderate moderate low9 Flowering ability present present present present10 HCN potential high moderate low moderate11 Poundability mealy Slightly mealy Non-mealy mealy12 Pubescence little moderate high moderate 13 Root color white white yellow white

Class activity: Identify 5 specific breeding objectives and select potential parents for possible hybridization activities

Format for different trial stages

S/N Trial

rep loc Plot size spacing Design

1. SN nil single 20m block 1m x 0.25m

2 CET nil single 6X1 1m x 0.8m Augmented

3 PYT 2 1-2 7x2 1m x 0.8m RCBD

4 AYT 4 2-3 7x4 1m x 0.8m RCBD

5 UYT 4 4 7x6 1m x 0.8m RCBD

6 NCRP 4 8-10 6x6 1mx1m RCBD

Parameters evaluated at different trial stages

- Seedling Nursery

- Root number- Dry matter on selected plants- Plant type- Mealiness on selected plant- Yield (visual) high/low - DM by mouth or feel - Diseases score - Total Carotene Chart

- Clonal evaluation- yield trials (PYT, AYT, UYT)- Sprout count and vigour at 1MAP- Disease evaluation at 1MAP: CMD- Diseases 3MAP: CMD, CBB- Diseases 6MAP: CMD, CBB, CAD, - Diseases 9 MAP: CAD, CGM- Visual rating 6MAP- Pre- harvest (1 week before harvest)- Harvest at 12MAP yield and yield related parameters)

Final genotype selection• Use appropriate selection index to rank and select desirable

genotypes• CBU, IITA uses selection index that incorporates the

following to generate index rank - DYLD = 60%- CMD =25%- HI = 15%

This index rank is then compared with the pre-harvest visual rating

Description Evaluation time

Scoring scale and Description

Plant type 12MAP 1= Cylindrical, 2= Umbrella, 3= Open, 4= compact

Lodging 12MAP 1= about 90% of plant are erect with no sign of root exposure 2=50% of plants not standing upright 3= 80% 0f the plant bent with roots exposed

Branching 12MAP 1= No branching at all2= branching height above 1.5m 3= branching height at 1m to 1.5m 4= branching height at 0.5m - 1.0m 5= branching height at 0.5m

visual rating

12MAP 1= excellent plant architecture, no sign of lodging and is CMD free2= very good architecture, CMD free, no lodging and good vigour3= desirable plant architecture, no visible sign of CMD, no lodge and good vigour4= undesirable plant architecture, moderate vigour, moderate disease severity and moderate level of lodge5= poor vigour, undesirable plant architecture,

Take home tips• Be vigilant on the field• Have the eye of a breeder• Understand trial objective/s• Ask qusetions when/if necessary• Follow established protocol of activity• Proper field labelling• Do a check list before embarking on field activity• Learn from previous mistakes and avoid such in future• enhance your intellectual capability and capacity• quality data capture helps to enhanced research

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Thanks for listening